BRIEF [O.A.] Theszóll, Charles Author: Theszóll, Charles Recipient: Haeckel, Ernst Dating: 23-02-1900
BRIEF OHNE UMSCHLAG Haeckel, Ernst Author: Haeckel, Ernst Recipient: Haeckel, Charlotte Dating: 05.05.1873
BRIEF [O.A.] Deregi, Oskar Author: Deregi, Oskar Recipient: Haeckel, Ernst Corporation: Nemzeti Szinház Dating: 11.09.1904